Whenever you find you need some helpers to get passed a level, items in the shop are options. There are plenty of things you can buy. From barcode scanner to air-condition, everything has its own benefit. Check out the description to see the effect of each item.
You can spend either coins or diamonds to buy items. Coins are obtained as a bonus of each level you played. Diamond is purchasable or obtained for FREE, ask your friends to send you.